The present invention is directed to expansible chamber devices and, in particular, to expansible chamber devices in which working members comprise alternately approaching and receiving elements. The invention finds particular application in devices such as alternating piston rotary internal combustion engines, pumps, and fluid motors. One embodiment of the invention relates to braking systems for controlling the motion of the working members in an expansible chamber device, including control of the intermittent rotation of the alternately approaching and receding elements used to define one or more expansible chambers. Another embodiment of the invention relates to a rotating piston synchronizing system for controlling the maximum extent of relative rotational motion between pairs of alternately approaching and receding elements of the expansible chamber device to enable the device to be easily started from an at-rest condition. A still further embodiment relates to a rotating piston synchronizing system for varying the timing of the working members in expansible chamber devices to adjust the compression ratio within the device.
Expansible chamber devices generally operate by changing the volume defined between working members in order to compress a working fluid or gas. One form of known expansible chamber devices, for example, is that disclosed in U.S. Pat. No. 4,279,577. There, the device incorporates a pair of opposed rotating members comprising one or more radially extending vanes or abutments to define, in part, an expansible chamber. Each of these members undergoes intermittent and alternating motion throughout the cyclic operation of the engine or pump. In devices of this type, the movement of the rotating members must be carefully controlled and synchronized. In the past, this control has been accomplished using control mechanisms which are complex in design and operation and which may be unreliable at higher operating speeds.
In U.S. Pat. No. 4,605,361, an oscillating vane rotary pump or motor uses a drive pin adapted to engage helical slots defined in coaxial rotor shafts and cam rollers to provide for oscillating the rotors and vanes with respect to each other as the rotors rotate with respect to the rotary pump or motor cylinder. In that system, a stationary cam is needed to permit the two pistons to rotate continuously as the output, or input in a pump, shaft rotates. Accordingly, that device is of little use in expansible chamber devices of the type including rotating pistons that intermittently rotate in the same direction during recurrent periods of rotation with each of the piston assemblies being stopped between the periods of rotation.
Sets of non-circular gears are used to control the relative positions of the rotating pistons in U.S. Pat. No. 5,381,766. The gears in that system, however, are difficult and expensive to manufacture and, further, do not provide a uniform output on the shaft.
An additional problem in devices of this kind is the inability to provide an adjustable compression ratio. There is a further need to provide an adjustable compression ratio during operation of the device.
A further problem in devices of this type is the difficulty in starting the devices from a stopped or at rest condition. Typically, various mechanisms within the device must be manually oriented into proper position before the output shaft(s) can be rotated in a starting mode of operation.
It would, therefore, be desirable to provide a device for controlling the motion of the working members in an efficient and simple fashion which solves the problems recognized in the prior art. It would further be desirable to provide a device for controlling the relative angular position between the working members to be constrained within a limited predetermined range for purposes of synchronizing them at start up when the expansible chamber device is used as an engine. It would additionally be desirable to provide a device for controllably adjusting the relative angular position between the working members to provide a variable compression ratio. Preferably, the compression ratio is adjustable either at a stop or while the device is functioning.
The aforementioned problems and others are addressed by the present invention described in detail in this specification.